Strange Vintage 2 Speed Mini-Bike

[Blazkowiez]

Okay, I wanted to get your opinion/info on this little bike. I understand this is not mini-bike forums and they would be the ones to identify it. We're obviously going to sell it but I'm not trying to sell it here just looking for thoughts on this set-up. We don't run across it very often because torque converters basically made them obsolete but that's life.

I threw in some pictures of it so people can bask in the glory of dual speed drive. I'm sure it'll find its way somewhere, a great deal of the bikes we've been selling have been finding their way to Austin more recently. Must be some sort of retro surge.

 

[oscaryu1]

They used to sell these two-speed setups IIRC...

 

[Blazkowiez]

Yes, they did. Comet made these, many heath kit bikes came with them but after 1960 they died out very quickly.

 

[T-man]

that is interesting I would like to know how they did that.
hey blaz when you start to clean it up take some more pics of it because I want to see how they had that set-up work.

 

[sideways]

Soooooo you gona tell us how it works?

Thanks

Hayden

 

[Pellethuntr2]

soooooo you gona tell us how it works?

Thanks

hayden

dito

 

[KieranM]

reminds me of the duplex chain.

 

[Blazkowiez]

It works by the first clutch which engages from the engine at the first ratio around 2,000 rpm(just like a normal clutch). This gives a solid take-off. The second clutch is a stall clutch which has a separate ratio which would act almost as if it were shifting simply by engaging. Once the second clutch which resides on the jack-shaft engages (depending on how far they set the stall 2600-3200) both clutches are locked up and the jack-shaft is forced to run on the lower ratio giving it a sort of overdrive. Its an older system but one that many people prefer over a torque converter but still kinda died out a very long time ago for the most part.

 

[porsche930dude]

yup those work pretty good. Thats a montgomory wards / gilson bike . You should check out Oldminibikes.com . lots of info on those

 

[Blazkowiez]

Cool man, thanks for that information. We see all kinds of bikes like that go through the shop, I just thought some people here would think it was neat to see the set-up since it is not fairly common from my experiences. I may actually sign up, it takes me a while to be willing to do things like this online with my limited spare time. I do appreciate the make info. I was thinking it was perhaps a HeathKit.

 

[Kenny_McCormic]

Last I checked, these setups and the parts are still available.

 

[Blazkowiez]

Kenny, you're right. You can still construct this set-up fairly easily and buy replacement parts. That does not however make it stock.

 

[motor_head]

It works by the first clutch which engages from the engine at the first ratio around 2,000 rpm(just like a normal clutch). This gives a solid take-off. The second clutch is a stall clutch which has a separate ratio which would act almost as if it were shifting simply by engaging. Once the second clutch which resides on the jack-shaft engages (depending on how far they set the stall 2600-3200) both clutches are locked up and the jack-shaft is forced to run on the lower ratio giving it a sort of overdrive. Its an older system but one that many people prefer over a torque converter but still kinda died out a very long time ago for the most part.

the second clutch is just like a normal clutch but engages at somewhere around 1600 rpm. the jack shaft actually spins the shoes. so when the engine gets up to 3600 rpm the jack shaft is spinning 1800rpm (because the ratio in 1st gear is 2-1) and the second clutch engages. then rpms go down (if the second clutch was dependent on engine speed this wouldn't happen and it wouldn't give as wide a range of speed) the second clutch stays engaged even when the engine slows because the jack shaft is now spinning 1-1 with the engine and the jack shaft rpm is still spinning around 2000 rpm.

 

[Blazkowiez]

The first clutch is on the motor itself and like all normal clutches would begin to engage at 2,000 rpm correct? How can the jack-shaft engage period if it has no means rotation? I am fairly new to this set-up clearly but please explain further so I can make sense of what you are telling me. I always enjoy learning new things here its fun.

 

[700 efi guy]

It works by the first clutch which engages from the engine at the first ratio around 2,000 rpm(just like a normal clutch). This gives a solid take-off. The second clutch is a stall clutch which has a separate ratio which would act almost as if it were shifting simply by engaging. Once the second clutch which resides on the jack-shaft engages (depending on how far they set the stall 2600-3200) both clutches are locked up and the jack-shaft is forced to run on the lower ratio giving it a sort of overdrive. Its an older system but one that many people prefer over a torque converter but still kinda died out a very long time ago for the most part.

in overdrive would both chains still be turning?

 

[Blazkowiez]

The first clutch doesn't stop being locked up when the second clutch engages my friend.

 

[700 efi guy]

so could you build this with 2 clutches, 1 on the motor and 1 on a live jack shaft, with the smaller axle sprocket going to the jack shaft clutch and a bigger axle sprocket to a sprocket on the jack shaft? there'd be a total of 3 chains, or would it all bind up?

 

[Blazkowiez]

Nothing binds up, as long as the clutches are not worn to the point where the bushings or springs are spent everything works great on these set-ups.

 

[r97]

the second clutch is set to engage at somewhere around 1800 rpm. it's that way because the shoes it the clutch are driven by the jackshaft with in 1st gear operates at 1/2 engine speed

i personally found the above descriptions of how it works to be slightly confusing (no offense to blaz or motor head).

my personal understanding is that there is an average clutch on the engine out put with 2 sprockets on it instead of just one, the first chain goes from the engine clutch to the large sprocket on the jack-shaft, this large sprocket has a built-in free-wheel device. the second gear is setup in a way so that the second chain coming from the engine clutch goes to a sprocket welded to the shoe assembly on the jack-shaft (not the drum like in a normal cent clutch) the shoe assemble on the jack shaft is also on bearings and has more spring tension so that it only engages when the jack-shaft is spinning near its max rpm, the jack-shaft clutch shoes expand and lock onto a drum fixed to the jack shaft, now the second gear is engaged, second gear spins faster than 1st so the free-wheel releases ands spins freely on the jack shaft. at the other end of the jack shaft is another sprocket which simply runs to the wheel. so engine cent clutch engages spinning both 1st and 2nd gear chains, first gear chain (roughly a 2 to 1 ratio) moves the free-wheel sprocket on the jack shaft faster than the shaft thus engaging the free-wheel and 1st gear along with it. next the engine revs to higher rpm which engages the second gear clutch which grabs onto a drum that is fixed to the jack-shaft(the heavier springs in this clutch make it engage only at high rpm), the second gear has a roughly 1 to 1 ratio so the jack shaft is now going to spin faster than the 1st gear free-wheel sprocket, when this happens it dis-engages the free-wheel. if you really wanted to you could install a free-wheel on the jack-shaft clutch drum and put on another, and another until you ran out of money, this would be quite bulky but would be fun! (every drum except for the last gear would have to be a free wheel though, also you would need to setup a second jack-shaft installed for chain alignment)

so sry about the all the writing but it is a full description, it would be alot easier to explain to you in-person with it in my hand, this pic should help.

also some good pics on this site, http://www.rcdon.com/html/grv-1_turbotug_project_12_01_0.html

p.s. blaz that looks like it will be a fun mini once its done!

 

[Blazkowiez]

It'll be a good project for whomever purchases it, as I said it'll most likely go to someone in Austin... they seem to love the mini-bikes there.